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feat(dsl): extend PTN_BIND to 10 names via chained macros #44

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Merged
sentomk merged 1 commit into from
Aug 1, 2026
Merged

feat(dsl): extend PTN_BIND to 10 names via chained macros #44

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2 changes: 1 addition & 1 deletion docs/api.md
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Original file line number Diff line number Diff line change
Expand Up @@ -223,7 +223,7 @@ $[rng(0, 10)]
$[rng(0, 10, pat::mod::open)]
```

`PTN_BIND` supports one to five names and can be declared at namespace or block
`PTN_BIND` supports one to ten names and can be declared at namespace or block
scope. Use callables for domain logic that does not read naturally as `_` or a
short named-placeholder expression.

Expand Down
71 changes: 48 additions & 23 deletions include/ptn/patternia.hpp
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Expand Up @@ -110,38 +110,58 @@ namespace ptn {
// A future reflection-based variant may validate this at compile
// time.
//
// Supports 1 to 5 member names.
#define PTN_BIND_1(Type, m0) \
constexpr ::ptn::pat::mod::arg_t<0> m0 { \
}
// Supports 1 to 10 member names.
//
// Implementation notes:
// - PTN_BIND_DECL declares a single named placeholder.
// - PTN_BIND_N is defined by chaining: it expands to
// PTN_BIND_{N-1} plus one more declaration, so adding a new
// arity only costs one short macro instead of a full rewrite.
#define PTN_BIND_DECL(Index, name) \
constexpr ::ptn::pat::mod::arg_t<Index> name{};

#define PTN_BIND_1(Type, m0) PTN_BIND_DECL(0, m0)

#define PTN_BIND_2(Type, m0, m1) \
constexpr ::ptn::pat::mod::arg_t<0> m0{}; \
constexpr ::ptn::pat::mod::arg_t<1> m1 { \
}
PTN_BIND_EXPAND(PTN_BIND_1(Type, m0)) \
PTN_BIND_DECL(1, m1)

#define PTN_BIND_3(Type, m0, m1, m2) \
constexpr ::ptn::pat::mod::arg_t<0> m0{}; \
constexpr ::ptn::pat::mod::arg_t<1> m1{}; \
constexpr ::ptn::pat::mod::arg_t<2> m2 { \
}
PTN_BIND_EXPAND(PTN_BIND_2(Type, m0, m1)) \
PTN_BIND_DECL(2, m2)

#define PTN_BIND_4(Type, m0, m1, m2, m3) \
constexpr ::ptn::pat::mod::arg_t<0> m0{}; \
constexpr ::ptn::pat::mod::arg_t<1> m1{}; \
constexpr ::ptn::pat::mod::arg_t<2> m2{}; \
constexpr ::ptn::pat::mod::arg_t<3> m3 { \
}
PTN_BIND_EXPAND(PTN_BIND_3(Type, m0, m1, m2)) \
PTN_BIND_DECL(3, m3)

#define PTN_BIND_5(Type, m0, m1, m2, m3, m4) \
constexpr ::ptn::pat::mod::arg_t<0> m0{}; \
constexpr ::ptn::pat::mod::arg_t<1> m1{}; \
constexpr ::ptn::pat::mod::arg_t<2> m2{}; \
constexpr ::ptn::pat::mod::arg_t<3> m3{}; \
constexpr ::ptn::pat::mod::arg_t<4> m4 { \
}
PTN_BIND_EXPAND(PTN_BIND_4(Type, m0, m1, m2, m3)) \
PTN_BIND_DECL(4, m4)

#define PTN_BIND_6(Type, m0, m1, m2, m3, m4, m5) \
PTN_BIND_EXPAND(PTN_BIND_5(Type, m0, m1, m2, m3, m4)) \
PTN_BIND_DECL(5, m5)

#define PTN_BIND_7(Type, m0, m1, m2, m3, m4, m5, m6) \
PTN_BIND_EXPAND(PTN_BIND_6(Type, m0, m1, m2, m3, m4, m5)) \
PTN_BIND_DECL(6, m6)

#define PTN_BIND_8(Type, m0, m1, m2, m3, m4, m5, m6, m7) \
PTN_BIND_EXPAND(PTN_BIND_7(Type, m0, m1, m2, m3, m4, m5, m6)) \
PTN_BIND_DECL(7, m7)

#define PTN_BIND_9(Type, m0, m1, m2, m3, m4, m5, m6, m7, m8) \
PTN_BIND_EXPAND(PTN_BIND_8(Type, m0, m1, m2, m3, m4, m5, m6, m7)) \
PTN_BIND_DECL(8, m8)

#define PTN_BIND_10(Type, m0, m1, m2, m3, m4, m5, m6, m7, m8, m9) \
PTN_BIND_EXPAND( \
PTN_BIND_9(Type, m0, m1, m2, m3, m4, m5, m6, m7, m8)) \
PTN_BIND_DECL(9, m9)

#define PTN_BIND_PICK(_1, _2, _3, _4, _5, NAME, ...) NAME
#define PTN_BIND_PICK( \
_1, _2, _3, _4, _5, _6, _7, _8, _9, _10, NAME, ...) \
NAME

// Extra indirection layers for MSVC traditional preprocessor
// compatibility. Without these, MSVC treats __VA_ARGS__ as a single
Expand All @@ -154,6 +174,11 @@ namespace ptn {
#ifndef PTN_BIND
#define PTN_BIND(Type, ...) \
PTN_BIND_DISPATCH(PTN_BIND_EXPAND(PTN_BIND_PICK(__VA_ARGS__, \
PTN_BIND_10, \
PTN_BIND_9, \
PTN_BIND_8, \
PTN_BIND_7, \
PTN_BIND_6, \
PTN_BIND_5, \
PTN_BIND_4, \
PTN_BIND_3, \
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70 changes: 70 additions & 0 deletions tests/tests_named_placeholder.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,19 @@ namespace {
int e;
};

struct Deca {
int a;
int b;
int c;
int d;
int e;
int f;
int g;
int h;
int i;
int j;
};

// Declare named placeholders for each struct.
// These are constexpr arg_t<N> objects.
PTN_BIND(Point, x, y);
Expand All @@ -54,6 +67,7 @@ namespace {
PTN_BIND(Single, sv);
PTN_BIND(Quad, qa, qb, qc, qd);
PTN_BIND(Penta, pa, pb, pc, pd, pe);
PTN_BIND(Deca, da, db, dc, dd, de, df, dg, dh, di, dj);

} // namespace

Expand Down Expand Up @@ -381,3 +395,59 @@ TEST(NamedPlaceholder, BindFourArgGuardFails) {
ptn::_ >> 0);
EXPECT_EQ(result, 0);
}

// =========================================================================
// PTN_BIND arity coverage: 10 member struct (chained expansion).
// =========================================================================

TEST(NamedPlaceholder, TenMemberTypeCorrect) {
static_assert(std::is_same_v<std::decay_t<decltype(da)>,
ptn::pat::mod::arg_t<0>>);
static_assert(std::is_same_v<std::decay_t<decltype(dj)>,
ptn::pat::mod::arg_t<9>>);
}

TEST(NamedPlaceholder, TenMemberGuard) {
// a + b + ... + i == j
Deca d{1, 1, 1, 1, 1, 1, 1, 1, 1, 9};
auto result = ptn::match(d)
| PTN_ON(
ptn::$(
ptn::has<&Deca::a,
&Deca::b,
&Deca::c,
&Deca::d,
&Deca::e,
&Deca::f,
&Deca::g,
&Deca::h,
&Deca::i,
&Deca::j>)[da + db + dc + dd + de
+ df + dg + dh + di
== dj]
>> 1,
ptn::_ >> 0);
EXPECT_EQ(result, 1);
}

TEST(NamedPlaceholder, TenMemberGuardFails) {
Deca d{1, 1, 1, 1, 1, 1, 1, 1, 1, 10};
auto result = ptn::match(d)
| PTN_ON(
ptn::$(
ptn::has<&Deca::a,
&Deca::b,
&Deca::c,
&Deca::d,
&Deca::e,
&Deca::f,
&Deca::g,
&Deca::h,
&Deca::i,
&Deca::j>)[da + db + dc + dd + de
+ df + dg + dh + di
== dj]
>> 1,
ptn::_ >> 0);
EXPECT_EQ(result, 0);
}
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